S355JR is a widely used non-alloy structural steel produced under EN 10025-2, known for its high tensile and yield strength, excellent weldability, and good impact resistance. It is suitable for harsh environments and heavy-load applications across construction, bridge engineering, machinery, and shipbuilding. Its combination of mechanical strength and processing performance makes it one of the most specified structural grades in the world.
What Is S355JR Steel Plate?
S355JR is a non-alloy structural steel defined by EN 10025-2, with a minimum yield strength of 355 MPa for thicknesses up to 16 mm. The JR designation indicates Charpy V-notch impact testing at +20 degrees Celsius with a minimum absorbed energy of 27 J. It belongs to the S family of structural steels that also includes S235 and S275, which share the same designation logic with different strength levels. S355JR is supplied as plate, section, and bar, and is used where higher load-bearing capacity than S275 is required.
Mechanical Properties
The key mechanical properties of S355JR plate are a minimum yield strength of 355 MPa for the thinner range, decreasing stepwise with thickness per EN 10025-2, and a tensile strength range of 470-630 MPa for the common thickness range. The minimum elongation is about 22% for typical plate thicknesses, and the minimum impact energy is 27 J at +20 degrees Celsius. Typical hardness is in the range of 140-180 HB. The combination of strength and ductility supports cold forming and welding without loss of mechanical integrity.
Cutting and Machining
S355JR plate can be processed by drilling, milling, turning, laser cutting, and plasma cutting. The key parameters to control are cutting force, surface roughness, and processing efficiency, and the cutting speed and feed rate should be adjusted according to the plate thickness to achieve optimal results. Proper parameter selection reduces tool wear, improves surface finish, and increases production efficiency. For thick plates, preheating before flame or plasma cutting may be advisable to avoid hardening of the cut edge, depending on the cutting practice and the subsequent fabrication steps.
Forming and Welding
The formability of S355JR determines how well the material can be shaped without cracking or losing strength. Cold bending and hot bending produce smooth plastic deformation with predictable stress distribution, and stretching is suitable for shaping curves or cylindrical structures. The excellent plasticity of the grade allows complex shapes without compromising mechanical integrity. For welding, S355JR offers excellent weldability and is compatible with other structural steels. It supports MIG, TIG, and arc welding methods, and with proper parameters the weld area microstructure remains uniform with minimal risk of cracking or brittleness after welding. Proper preheating and controlled heat input improve toughness and prevent weld defects, especially for thick sections or cold environments.
Applications and Durability
S355JR plate is widely used across multiple industries. In construction it is used for structural beams, frames, and load-bearing elements; in bridges and infrastructure for highway, railway, and pedestrian bridges; in machinery manufacturing for heavy-duty frames and components; and in shipbuilding and offshore structures exposed to high stress and humidity. The grade offers good corrosion resistance in humid and rainy environments and sufficient surface hardness for long service life in industrial applications. Its durability makes it suitable for bridges, transmission towers, ships, and machinery operating in demanding conditions.
Frequently Asked Questions
What is S355JR equivalent to? S355JR has functional equivalents in other standards, including Q345B under the old Chinese standard GB/T 1591-2008, A572 Grade 50 in the ASTM system, ST52-3 in the old DIN system, and SM490B under JIS. Each is defined by its own standard, and exact properties should be verified before substitution.
What is the difference between S275JR and S355JR? S275JR offers a minimum yield strength of 275 MPa for thicknesses up to 16 mm, while S355JR provides a higher minimum yield strength of 355 MPa, making it ideal for projects requiring greater load-bearing capacity.
What does the JR designation mean in S355JR? The JR designation means the material has been subjected to a Charpy V-notch impact test at +20 degrees Celsius and has a minimum impact energy of 27 J, guaranteeing ductile behavior at room temperature.
Can S355JR be welded? Yes. S355JR has excellent weldability and is compatible with other structural steels. It supports MIG, TIG, and arc welding methods, with proper preheating and controlled heat input recommended for thick sections.
What cutting methods are suitable for S355JR plate? Common methods include laser cutting, plasma cutting, and flame cutting, as well as drilling, milling, and turning for machining operations. Cutting speed and feed rate should be adjusted according to plate thickness for optimal results.
Where is S355JR steel plate commonly used? It is used in construction beams and frames, highway and railway bridges, heavy machinery frames, and shipbuilding and offshore structures, where its combination of strength, weldability, and impact toughness is required.